# Can anyone help with this error? (I just want to see the contour of the bluish area at the bottom of the image)

2 views (last 30 days)
muhammad choudhry on 27 Jun 2020
Commented: darova on 3 Jul 2020
close all
clear all
clc
imshow(I)
imcontour(I,3)
Error:
Error in imcontour>ParseInputs (line 110)
validateattributes(a,{'uint8','int16','uint16','double','logical','single'}, ...
Error in imcontour (line 40)
[x,y,a,extra_args] = ParseInputs(varargin{:});
Error in contour (line 8)
imcontour(I,3)

darova on 1 Jul 2020
Detect blue region properly
I1 = double(I0);
% colors from blue region
R = [80 50 0];
G = [160 110 70];
B = [180 120 70];
B1 = logical(I1(:,:,1)*0);
% detect regions and merge
for i = 1:length(R)
B0 = abs(I1(:,:,1)-R(i)) < 20 & ...
abs(I1(:,:,2)-G(i)) < 50 & ...
abs(I1(:,:,3)-B(i)) < 50;
B1 = B1 | B0;
end
% B1 = uint8( cat(3,B1,B1,B1) );
imshowpair(I0,B1)
% imshow(B1.*I0)

darova on 3 Jul 2020
binarize image
A1 = im2bw(A0);
sum(~A1(:))
muhammad choudhry on 3 Jul 2020
You the man! seriously..... It worked
ans = 431
just wondering when I counted manually answer was 486 and with binarizing 431... differrence in pixels are like 55. Do you know why there is that difference?
sum(~A1(:)) => means it is adding all the pixels in the image except white background
darova on 3 Jul 2020
try to change threshold
th = graythresh(I0);
I1 = im2bw(I0,th);
imshow(I1)

Ameer Hamza on 27 Jun 2020
You need to specify a single channel image to imcontour(). For example, just provide the blue channel
imcontour(I(:,:,3), 3)
or convert image to grayscale
imcontour(rgb2gray(I), 3)

#### 1 Comment

muhammad choudhry on 29 Jun 2020
Hi,
Hamza please see the attached. I have changed to grey scale function to capture the contour of the injected dye flow but I am also getting the contours of other background is there a way to only capture the dye contour.
here is a code I used!
close all
clear all
clc
%Convert to greyscale (contour command works on greyscale images)
img=rgb2gray(I);
img1=rgb2gray(I1);
%Subtraction of the frames
figure()
dif=img-img1;
imshow(dif)
hold on
% contour of the image
figure()
imcontour(dif,1);